282 FROM NEBULA TO NEBULA 



the water in the well is just 10 fathoms deep. Clearly, 

 there would ensue an interesting race between the ten 

 substances for the bottom, in which contest the test of 

 fitness would, of course, be that of weight, or more tech- 

 nically speaking, specific gravity; and when the affair 

 has been concluded we shall find, piled up on the bottom, 

 a column of ten thin layers ranged in the order of their 

 heaviness. But what of the status of the race at its 

 various stages? In the first fathom, beginning at the 

 top, we shall see all the ten minerals inextricably mingled, 

 but in this stretch the lightest of all will become so dis- 

 tanced that in the second fathom we shall be able to dis- 

 tinguish but nine sorts, in the third but eight, and so on 

 until the heaviest particles begin to touch bottom. 



Now, something of this sort occurs in the shell of the 

 sun, except that here the tests of fitness are two instead 

 of only one, and these two are, first, specific gravity 

 (perhaps it were more accurate in this case to say atomic 

 weight}, and, second, refractoriness, or resistance to vol- 

 atilization. Imagine now, if you please, the earth 

 ground into fine powder and sprinkled over a limited area 

 of the solar surface, and for the sake of simplicity sup- 

 pose, further, this powder to be classifiable into ten dis- 

 tinct grades, as in our previous illustration, and, lastly, 

 suppose the solar shell to be likewise differentiated into 

 ten successive strata with temperatures progressing 

 downwardly. Is it not obvious, now, that there would 

 here ensue a process of distillation, a sort of refining or 

 smelting process, in which the diverse materials would, 

 in the order of their volatility, be successively driven off 

 as they sank (by reason of their avoirdupois) into lower 

 and lower levels of higher and still higher temperatures? 

 It follows, then, as a matter of deduction, that the lining 

 of the central chamber of the sun, or shall we say its face- 

 wall, is almost, if not quite, homogeneous and composed 

 of a substance all but perfectly refractory, and that 

 thence on outward the layers gain steadily in heterogene- 

 ity until we reach the surface. 



In this process we see that the sun is something more 

 than a dispenser of light and heat ; he is also a smelter of 



